1. Field
The present invention relates to a compound having a xanthene structure, a coloring composition containing a copper compound, an ink for inkjet recording and an inkjet recording method.
2. Description of the Related Art
An inkjet recording method is a method of printing by dispersing an ink droplet and attaching it to a recording medium such as paper as known in the related art. By this printing method, it is possible to print a high-resolution and high-quality image conveniently at a high speed. In particular, in color printing, a technical development has been recently performed for an image forming method which can replace photographs.
In the case of forming a color image by using an inkjet recording method, it is common to use a yellow ink, a magenta ink, a cyan ink and a black ink. Conventionally, water-based inks have been mainly used as these inkjet inks in terms of safety, such as malodor and hazard associated with fire-fighting. These inks are required to fail within suitable ranges in viscosity, surface tension, and the like, to be excellent in nozzle clogging and storage stability, to impart a recording image at a high concentration, and to be excellent in light fastness, ozone fastness, water fastness and moisture fastness.
Such a performance is mostly satisfied by using a water-based ink containing water or a mixture of water and a water-soluble organic solvent as a main solvent. However, characteristics such as hue, brighteness, light fastness, ozone fastness, water fastness and moisture fastness are influenced considerably by colorants and additives, and various dyes have conventionally been studied.
As a water-based ink capable of realizing a recording image having excellent light fastness, an ink has been reported, which contains a specific metal compound in the ink. Japanese Patent Application Laid-Open No. 2002-533524 (hereinafter JP-A-2002-533524) discloses an ink composition containing a colorant and a specific metal salt. Japanese Patent Application Laid-Open No. 2011-195782 (hereinafter JP-A-2011-195782) discloses an ink composition containing a specific anthrapyridone-based dye and a copper compound that is soluble in water.
However, the inks described in JP-A-2002-533524 and JP-A-2011-195782 do not sufficiently exhibit all the performances such as hue, ozone fastness and light fastness, which are required for use as an inkjet ink.
An object of the present invention is to provide a coloring composition capable of improving light fastness without deteriorating hue and ozone fastness.
The present inventors have intensively studied for a coloring composition capable of improving light fastness without deteriorating hue and ozone fastness, and have found out that the above-mentioned problems can be solved by a coloring composition containing a coloring compound having a specific structure as exemplified below and a copper compound, which is not described in JP-A-2002-533524 and JP-A-2011-195782. Further, the present inventors have intensively studied and have fount out that an unexpected effect that the coloring composition has an excellent stability over time as well can be obtained.